After the customer account details are stored, as part of the initial transaction/registration, you will need to keep a record of the associated registration IDs (token) that you can then use in step 1 below.

1. Prepare the checkout

NOTE: For demonstration purposes we have created a registration, which will be used in your one-click checkout, with id(s): 8ac7a4a26ae987c9016aefae0c741093,8ac7a49f6ae9098f016aefae0e601cc8. Following the guides above, you may add additional registrations options to the checkout.

First perform a server-to-server POST request to prepare the checkout, this should include the registration IDs of the customer as shown below.

The registration IDs should be sent in the registrations[n].id parameter, where n is a sequence number from zero, incrementing for each of the customer's registration IDs. For example, if the customer has two accounts on file, you would send registrations[0].id = {first registration.id} and registrations[1].id = {second registration.id}.

2. Create the payment form

Then, to show the payment form you just need to add the following lines of HTML/Javascript to your page and populating the following variables